mob farms do not exploit any known bug, glitch, or cheat. they are creative uses of known resources, perfectly legal

Fact. If you can build a little farm/grinder out of a spawner or spawners that you've found, it's perfectly ok. They've ruled that AFK coasters are not allowed, though, so you'll have to actually be there to keep mobs spawning, but otherwise there's nothing wrong with making a mob farm/grinder. And the others are also correct in that spawners can't be moved. Last time I checked, even if you could move them, they ended up just spawning pigs after being replaced.

Fact. If you can build a little farm/grinder out of a spawner or spawners that you've found, it's perfectly ok. They've ruled that AFK coasters are not allowed, though, so you'll have to actually be there to keep mobs spawning, but otherwise there's nothing wrong with making a mob farm/grinder. And the others are also correct in that spawners can't be moved. Last time I checked, even if you could move them, they ended up just spawning pigs after being replaced.